A high unmet need persists for successful delivery of nucleic acid therapy (e.g., DNA, RNA) to address genetic and epigenetic heterogeneity, which underlie current cancer therapy failures. Multifunctional nanotechnologies are recognized as promising delivery platforms; however, key limitations in effective delivery of functionally intact nucleic acid payloads and/or in safety impede clinical translation of current nucleic acid nano-delivery systems.1-4 Assuming tumor-specific targeting is achieved, efficacy of lipid and likely other nanoplatforms are dependent on endocytosis or macropinocytosis for intracellular delivery and remain inefficient due to limited (<2%) escape of nucleic acid-cargo from endosomes into the cytosol2,5 and/or due to majority (>70%) of internalized RNA-cargo being exocytosed back to the extracellular space.6 Moreover, even if delivered intact, DNA/RNA-payloads need to integrate into the cellular machinery for functional efficacy.2 Moreover, efficient in vitro nano-delivery systems, such as self-assembled cationic PEI-polyplexes, manifest toxic effects arising from excess cationic material remaining after self-assembly and/or from release of high MW or branched-PEI25kDa as a result of disassembly in vivo.4 Alternatively, sonoporation-induced cytosolic-delivery of nucleic acid therapies has been tested to bypass inefficiencies of endosomal uptake, but remains inefficient with current microbubble technologies and modifications.7, 60 To overcome key limitations, rational nanoparticle designs must consider not only charge, hydrophilicity, shape, and size8-13, but also the need to eliminate excess unincorporated materials, improve in vivo structural stability and prevent aggregation. Ideally, designs must also consider alternative endocytosis-independent mechanisms to deliver [DNA/RNA]-payloads,′ modular multifunctionalities,14 and inherent versatility to accommodate multiple targeting and payload moieties to address genetic/epigenetic heterogeneity in cancers, which to date, underlie current cancer therapy failures.
By virtue of their spatial separation of multifunctional components, thus eliminating confounding multi-component steric or chemical interactions, Janus nanoparticle designs have a unique potential to meet the foregoing criteria14,15 However, this potential has yet to be realized with Janus NPs reported to date, which are typically larger than 100 nm, and were not designed to deliver nucleic acid therapies.14-19 Alternatively, nano/micro-hybrids bring unexplored potential, however, while dual MRI-ultrasound imaging flexibility has been attained using “nano-in-micro” composites of iron oxide nanoparticles encapsulated within microbubbles2,14 or within the microbubble shell,20-22 these composite particles lack delivery functionality.